<template>
  <div class="pagination">
    <button :disabled="pageNo===1" @click="$emit('newPageNo',pageNo-1)">上一页</button>
    <button v-show="startEndPage.start>1" :class="{active:pageNo===1}" @click="$emit('newPageNo',1)">1</button>

    <button v-show="startEndPage.start>2">···</button>

    <button v-for="page in startEndArr" :key="page" :class="{active:pageNo===page}" @click="$emit('newPageNo',page)">
      {{page}}
    </button>

    <button v-show="startEndPage.end < totalPages - 1">···</button>
    <button v-show="startEndPage.end < totalPages" :class="{active:pageNo===totalPages}" @click="$emit('newPageNo',totalPages)">{{totalPages}}</button>
    <button :disabled="pageNo===totalPages" @click="$emit('newPageNo',pageNo+1)">下一页</button>

    <button style="margin-left: 30px">共 {{total}} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: ["totalPages", "pageNo", "continuePage",'total'],
  // mounted() {
  //   setTimeout(() => {
  //     console.log(this.startEndPage);
  //   }, 2000);
  // },
  computed: {
    startEndArr(){
      const arr = []
      for(var i = 1;i <= this.startEndPage.end;i++){
        if(i >= this.startEndPage.start){
          arr.push(i)
        }
      }
      return arr
    },
    /* 
      totalPages:总页数
      pageNo:当前页
      continuePage:连续页
    */
    startEndPage() {
      const { totalPages, pageNo, continuePage } = this;
      //根据当前页计算连续页
      let start = 0,
        end = 0;

      //判断总页数和连续页的多少比较
      if (totalPages < continuePage) {
        //如果总页数小于连续页,起始是1和结束是总页数
        start = 1;
        end = totalPages;
      } else {
        //如果总页数大于连续页
        //首先根据当前的页码,计算出连续页的开头 和 连续页的结尾
        start = pageNo - Math.floor(continuePage / 2);
        end = pageNo + Math.floor(continuePage / 2);

        if (start < 1) {
          //如果start小于1  则直接设置起始为1
          start = 1;
          //如果start已经变成1了 则直接设置end为连续页长度
          end = continuePage;
        }

        if (end > totalPages) {
          //如果end大于总页数,则直接设置end为总页数
          end = totalPages;
          start = totalPages - continuePage + 1;
        }
      }

      return { start, end };
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>